Refrigerated transport is required to maintain a cold chain for fresh produce such as flowers, vegetables, fruits, milk products, meat, fish and poultry, frozen foods such as ice cream and other temperature sensitive products such as chemicals, biological agents, explosives, etc. which have to be at least partly refrigeratedly transported. The refrigerated transport includes transport by light and heavy trucks, trains, containers, ships, aircraft, etc.
Distribution networks typically make use of such a refrigerated transport. Refrigerated goods are stocked in refrigerated refrigeration containers, conveyed to the shops and unloaded into the refrigerated space of the respective stores. This allows a cold chain to be guaranteed for 100%.
There are basically two types of refrigeration containers, namely active and passive refrigeration containers. In active refrigeration containers, the cooling is substantially carried out during the transport by a compressor, in which a cooling agent is circulated in the pipes of a cooler and evaporated, and the ambient air or a gas, for example nitrogen in a controlled atmosphere, is cooled.
Heat is withdrawn from a cooling (cold) area, whereby the circulating ambient air or the gas is getting colder. Optionally there is a circulation system present in, or associated with, the refrigeration container, for example, a fan, to advance the circulation of the ambient air, and thus the cooling rate. Such cooling systems have the disadvantage that they are dependent on a source of energy, in particular an electrical power source, optionally in combination with a diesel engine. As a result, active refrigeration containers are essentially immobile, expensive and maintenance prone. The advantage is that active refrigeration containers are not dependent on an extremely good insulation since the compressor can continue working until the desired cooling temperature is reached.
Passive refrigeration containers comprise a cooling system whereby no external power source is present during transport for taking care of the refrigeration. Thus, it is not possible to pump around or to evaporate a coolant. In a first embodiment, this may be active refrigeration containers which were disconnected from their power source. In another embodiment, these are refrigeration containers in which the cooling is carried out by a coolant which is present in the refrigeration container, and which allows for the cooling due to its physical properties, for example, by the sorption of zeolites or by a phase transition (solid/liquid/gas). Typical examples of the refrigeration on the basis of a phase transition, are refrigeration by ice, in particular binary or slurry-ice, for example, water-based, water/ethylene glycol mixtures, water/alcohol mixtures, or water/salt mixtures (eutectic mixtures); refrigeration by solid CO2 (CO2 snow, carbonic ice, dry ice), liquid CO2, acetone and liquid nitrogen. The coolant may be present in a separate container in the refrigeration container, or may be located in the wall, for example, in hollow channels, divided over the wall, into a hollow space in the wall, or in a double-walled cooling segment which forms the wall, or a part of it.
Such passive refrigeration containers are able to hold their desired cooling temperature only for a limited time which is why they must be provided with a very good insulation. Typically, such an insulation is provided in the form of polyurethane foam, which at the same time has a reinforcing function. In the production of such a refrigeration container, the polyurethane foam is sprayed in the space between the cooling element and the housing, so that, after the foaming and curing of the polyurethane foam, a solid insulating layer is obtained which bonds the housing to the cooling element, and grants the necessary strength.
The inventors have found that already under normal use, for example in distribution centers which intensively use large amounts of said passive refrigeration containers, passive refrigeration containers often need to be repaired. It particularly concerns repairs to the housing and the moving parts, in particular to the door of the refrigeration container. By the use of intensive large numbers of said passive refrigeration containers at the distribution center and by treatment thereof with manipulation devices such as forklift trucks, both the outer wall (the housing) as the inner wall are often crushed, with the result that the intermediate insulation is compressed and partially loses its insulating power. These repairs are labor intensive, and the quality of the repaired refrigeration container is never equivalent to that of an original because the two walls, which are usually glued together with PUR, must be drawn from each other, whereby the insulation is damaged, the dent in the insulation must be sprayed again and then everything should be reassembled. Such passive refrigeration containers from the prior art are in fact made not to be disassembled, or only occasionally, after assembly of the different parts, in particular the cooling element, the insulation and the housing. Often such containers with a severe defect are decommissioned instead of carrying out a difficult repair. In addition, the components, in particular the insulation and the housing, are not or hardly available as a separate part in order to be exchanged against the installed components.